Manufacture of hollow bodies from fibrous material pulp



July 31, 1928.

F. w. BAUMGARTNER MANUFACTURE HOLLOWBODIES FROM FIBROUS MATERIAL PULPFiled April 21, 1925 //v l/EA/ 702 i M W MM Patented July 31, 1928.

oNrrEo sures- 1,678,759 PATENT OFFICE.

FRIEDRICH WILHELM BAUMGARTNER, OF BERLIN-SCHIONEBERG", GERMANY, .AS-SIGNOR T0 F. A. BAUMGARTNER, DR. KATZ & CO. G. M. B. H., OFEISWERBER-SPAN- DAU, GERMANY.

MANUFACTURE OF HOLLOW BODIES FROM FIBROUS MATERIAL PULP.

Applicationfiled April 21, 1923, Serial No. 633,660, and in GermanyNovember 16, 1922.

The invent-ion relates to a method of manufacture of hollow bodies, forexample, packing material and useful articles of fibrous material pulpsuch as wood pulp, cellulose or textile fibers.

Processes are known, for example, using paper pulp, in which with theaid of a heated gaseous pressure medium such as compressed air, steamand the like, hollow bodies are produced in moulds with permeable walls.By none of these methods was is possible to manufacture hollow bodies ofany desired volume limited only by the size of the mould with smoothcardboard interior surfaces in an efficient manner. The condition of theinner surface, however, is, of particular importance for the generaluse, for example, in the packing of foods or for technical requirements.

The preliminary requirements for the production of smooth interiorsurfaces are as follows:

The moulding must be efi'ected so far as possible by hydrostaticpressure before the heated gaseous pressure medium drives the pulpagainst the permeable walls of the mould, presses out the superfluouswater and comes into contact with the wallsof the mould. It will beunderstood also that the process of moulding becomes all the moreefficient the less compressed air or steam is.

required.

During its moulding and drying action on the fibrous pulp, gyrations andpulsations of the gaseous pressure medium should be prevented becausethey result in roughening the interior surface. -This is attained on theone hand by the above mentioned limitation of the action of the gaseouspressure medium on account of the high percentage of hydrostaticmoulding. So fares the gaseous pressure medium is still required, it isintroduced in as uniform a manner as possible in a working directionwhich might be considered as running parallel to the walls of the mould.

In order to mould hollow bodies in cordanee with thesepreliminaryconditions, the procedure is as follows: A preliminarycontainer is interposed in front of the mould to take the fibrous pulp,the concentration of which should be as small as possible. Thepreliminary container is connected with the mould by an inlet pipe whichis to be dimenpreliminary container must he dimensioned of at least2,500 cubic centimetres capacity.

The hollow body to be moulded should have 500 cubic centimetres capacityand also accordingly the mould.

Of the 2,500 cubic centimetres of themeliminary container, since themould itself has only 500 cubic centimetres, 2,000 cubic centimetres arethrough the mould. The percentage of hydrostatic moulding amountshowever to about 80. If. however, and in order to obtain smooth interiorsurfaces this is to be aimed at, the percentage of hydrostatic mouldingis about 92 instead of 80, of the 500 cubic centimetres still 300 cubiccentimetres should be displaced hydrostatically. In order to accomplishthis without increasin g the preliminary container which perhaps inpractice cannot be done or at least would be burdensome, a furtherdevice is used. The inner space of the mould is diminished by a built-incentred body according to this numerical example of 300 cubiccentimetres capacity which should not touch the bottom of the mould.Furthermore, according to the process on which the invention is based,the favorable condition of hydrostatic moulding without increasing thepreliminary container can also be acomplished by the action of a pistonpressing in the mould.

Assumingthe above, the moulding according to the invention takes placeas follows:

The fibrous pulp is introduced into the preliminary container, usuallyautomatically, and flows from the preliminary container into the mould.Then the heated gaseous pressure medium is introduced in such a way thatit acts from above against the upper surface of the fibrous pulpintroduced for moulding in the described manner. The pulp flows almostparallel to the-walls of the mould therein so that gyrations at thepoint of entry or elsewhere are avoided and almost the whole of thefibrous material contained in the suspension is pressed against thewalls of the mould by hydrostatic moulding;

hydrostatically pressed any fibres still remaining in the suspension arethen distributed by air on the interior walls. After the moulding anddrying'the mould opens out and the hollow body provided now with smoothinterior surfaces is ready for use without requiring any subsequentdrying. v

In the drawing two constructional examples of the mould are showndiagrammatically in cross section and elevation. The fibrous pulp entersthrough the inlet pipe a into the preliminary container 12 and from thisinto the actual mould c. The introduction of the gaseous pressure mediumis effected through 6. A

The moulds are, as is well known, permeable to air. In Figure 2,retaining all parts of Figure 1, there is further centred in theinterior of the mould a body 7.

Having now particularly described and ascertained the nature of my saidinvention, and in what manner the same is to be performed, I declarethat What I claim is:

1. Apparatus for molding hollow pulp bodies having smooth interiorsurfaces comprising a lower, permeable mold, an upper container, a bodydisposed-in the mold to diminish the space within the 'mold, and

means for introducing gas under pressure into the container.

2. Apparatus for molding hollow pulp bodies having smooth interiorsurfaces comprising a permeable mold and a container connected together,a body disposed in the mold to diminish the space within the mold, andmeans for forcing a fluid, under pressure, upon the surface of pulpliquor in the container and the mold and between the body and the wallsof the mold and along the said walls from one end of the mold to theother end of the mold to force the pulp liquor hydrostaticallythroughthe container and into and against the walls of the mold and to causethe pulp liquor to travel along the walls of the mold from the said oneend of the mold towards the said other end of the mold, whereby thefibrous material of the pulp liquor is distributed along the walls ofthe mold and there dried by the heated gas.

In testimony whereof, I have hereunto subscribed my name this 16th dayof March,

FRIEDRICH WILHELM BAUMGARTNER.

